Mr Shorten, who held a town hall meeting in the Liberal-held seat of Stirling last night, will use his latest visit to WA to reveal an increase in Labor’s planned Fair Share for WA Fund.

When he originally announced the fund, Mr Shorten pledged it would lift WA’s GST share to a floor of 70¢ in the dollar at a cost of $1.6 billion.

The WA Treasury last month updated its forecasts on the State’s GST share, predicting it would fall short of 70¢ over the next three years.

Mr Shorten said that because of the new figures, Labor would increase the fund to $2 billion and take the commitment out to 2022-23.

The extra funds would be on top of the infrastructure spending announced in the most recent State Budget.

That spending, part of a special package revealed by Mr Turnbull in April, has been earmarked for a range of projects, including the Morley to Ellenbrook rail line and the Armadale to Byford rail extension.

Labor had committed to $1.2 billion worth of the Government’s package but with it now incorporated into the Federal and State budgets, it has moved to promise its WA fund over and above that on offer from Mr Turnbull.

Camera IconOpposition Leader Bill Shoten at a Town Hall meeting in Stirling last night.Picture: Twitter/ @billshortenmp

Mr Shorten said Labor would consider the findings of the Productivity Commission report into the GST, which has yet to be made public, but it was standing by its separate commitment to WA.

“We will help Western Australia without hurting the Eastern States — with more money and more certainty for the future,” he said.

“Federal Labor will now work with the West Australian Government and Premier Mark McGowan to finalise the investment priorities for the fund to build a brighter future for the West.”

The commitment potentially frees up money for the State Government to either sink directly into more infrastructure projects or help cover the cost of social programs.

Mr Shorten’s pledge comes while the Government continues to sit on the Productivity Commission review of the GST system.

Mr Turnbull has promised the report will be made public this month, well ahead of the “super Saturday” by-elections on July 28.

The by-elections include the seats of Fremantle and Perth, where the Liberal Party is not standing candidates.

It is understood Federal Treasurer Scott Morrison has yet to reveal details of the report to his State counterparts.